Conventionally, there are known arms for a construction machine, the arm including an arm top formed by casting, as shown in Patent Literatures 1 and 2. The arm top does not include any weld involving high stress concentration, which allows the arm top to have a high strength.
However, the techniques disclosed in Patent Literatures 1 and 2, involving integrally forming the entire arm top by casting, requires a large and complicated mold for the casting which is hard to produce and it is difficult to obtain high production accuracy.